This invention relates to a multi-layer composite structure, and in particular, to a composite structure having a plastic chemically bonded to the substrate of the composite structure to impart resistance to delamination when subjected to impact and/or thermal shock.
Many attempts have been made by industry to make a multi-layer composite structure including at least a substrate of appreciable strength and stiffness, wherein the layers are resistant to delamination when subjected to high impact or when subjected to thermal shock. When subjected to high impact from either side of the structure, one of the layers, the finish layer, may deform, crack, craze, or chip, and another layer, i.e., a plastic layer, may delaminate from the substrate. Delamination may also occur when the composite structure is subjected to thermal shock.
U.S. Pat. No. 3,172,775 discloses a structure of ceramic-coated asbestos fibers impregnated with a thermoplastic or thermosetting resin. The ceramic material, in the form of a frit, is fused to the asbestos fibers. The resin is allowed to impregnate the ceramic fibers to form a bond. In U.S. Pat. No. 3,496,058, a semi-elastic layer, containing particulate material such as sand, is applied to one side of an aluminum sheet, and to this layer, a plastic foam is applied. If the semi-elastic layer were not used, tthe aluminum would be dented if subjected to impact by a one-pound metal ball dropped through a distance of 3 feet. In U.S. Pat. No. 4,053,545, a thermoplastic sheet is reinforced by injecting a plastic foam into a mold. Bonding is achieved through melting of the thermoplastic sheet, or an adhesive coating is applied to the thermoplastic sheet to firmly bond the sheet to the foam. In U.S. Pat. No. 4,216,294, a rigid or semirigid structure, such as a fiberglass-reinforced polyester panel, for example in the form of a boat, has applied thereto a polyester foam. The polyester foam is used because of its excellent adhesion to a like material. U.S. Pat. Nos. 3,823,099 and 4,358,548 describe polyester-foam-resin systems which form both rigid and flexible open-or-closed-cell foam products. The foams can be employed in operations such as spray-up, hand-layup, press molding, expansion casting RIM or RRIM, and resin-transfer molding.